Chain stitch forming device for a lock stitch sewing machine

ABSTRACT

A chain stitch forming device is provided with a movable loop retaining member for retaining a thread loop released from the loop taker of a lock stitch sewing machine. After the needle which is to be brought down next time into the thread loop held by the retaining member has passed through the throat plate, the retaining member is so actuated as to release the thread loop by a separate operating means, thus enabling a chain stitch to be formed using a lock stitch sewing machine.

United States Patent Dec. 24, 1969, Feb. 18, 1970, Feb. 19, 1970 Japan44/40463, 44/70768, 44/97046, 44/104709, 45/15935 and 45/16443 CHAINSTITCH FORMING DEVICE FOR A LOCK Primary Examiner.lames R. BolerAttorney- Kemon, Palmer & Estabrook ABSTRACT: A chain stitch formingdevice is provided with a movable loop retaining member for retaining athread loop G released from the loop taker of a lock stitch sewingmachine. rawmg After the needle which is to be brought down next timeinto U.S.Cl 112/168, the thread loop held by the retaining member haspassed 1 12/201 through the throat plate, the retaining member is soactuated Int. Cl Db 1/14 as to release the thread loop by a separateoperating means, Field of Search ll2/l68, thus enabling a chain stitchto be formed using a lock stitch 181, 197,201 sewing machine.

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M 1 m, Mi W CHAIN STITCH FORMING DEVICE FOR A LOCK STITCH SEWING MACHINEThis invention relates to sewing machines, and more particularly, todevices for converting a lock stitch sewing machine to a chain stitchsewing machine. A sewing machine in common use is of a lock stitch type.It has been desired that the machine be also capable of forming chainstitches, if required. Although, to meet this demand, there have beenemployed various types of .chain stitch forming device, all of them werenot only complicated in mechanism and extremely expensive, but alsopresented considerable difficulties in manufacture and failed to beeasily fitted to the sewing machine. With some chain stitch formingdevice, loop taker parts of a lock stitch sewing machine, for example, abobbin case of its retainer had to be replaced by a separate memberadapted for the formation of chain stitches. This was not onlytroublesome to a general sewing machine user, but also most likelycaused such parts to be lost after such replacement.

It is an object of the present invention to provide a chain stitchforming device wherein there is disposed a movable loop retaining memberin the passage of a thread loop released from the loop taker and liftedby the takeup mechanism, thereby enabling good chain stitches to bealways formed without the skipping of stitches.

A further object of the invention is to provide a chain stitch formingdevice wherein the aforementioned movable loop retaining member isrotatably mounted on a restraining member for obstructing the circularmovement of the bobbin case retainer of the loop taker, so that saiddevice is of very simple construction and capable of being manufacturedeasily and at low cost and readily fitted to the frame of the sewingmachine.

A still further object of the invention is to provide a chain stitchforming device which always permits the formation of good chain stitchesdespite its simple construction, eliminates the necessity of replacingthe bobbin in forming chain stitches as has been required for the priorart device and allows a general sewing machine user to carry out chainstitching without any troublesome operation in advance.

For a lock stitch sewing machine provided with a loop taker involving abobbin case retainer so as to form lock stitches in cooperation with areciprocable needle, the present invention provides a chain stitchforming device equipped with a loop retaining member for retaining athread loop released from the loop taker, said loop retaining memberbeing actuated by a separate operating means to release the thread loopfor chain stitching after the needle has passed through the throat platewhich is to be brought down next time into the thread loop held by theretaining member, so that said device eliminates the necessity ofreplacing the bobbin case or its retainer in performing chain stitchingand can be manufactured easily and at low cost due to simpleconstruction and always permits the formation of good chain stitches.

This invention can be more fully understood from the following detaileddescription when taken in connection with reference to the accompanyingdrawings, in which:

FIG. I is a perspective view of an ordinary lock stitch sewing machinepermitting the use of a chain stitch forming device according to anembodiment of the present invention;

FIG. 2 is a similar perspective view of FIG. 1, showing by two dot-dashlines a frame including a loop taker rotatably mounted around ahorizontal axis and extending parallel with the direction in which thereis fed a work fabric;

FIG. 3 is an elevation of an entire chain stitch forming device, where athread loop released from a loop taker is retained by a loop retainingmember;

FIG. 4 is a sectional view on line 4-4 of the chain stitch formingdevice of FIG. 3;

FIG. 5 is a plan view of thereof; device of FIG. 3 taken from line 5-5thereof;

FIG. 6 is a sectional view on line 6-6 of the device of FIG.

FIG. 7 is a sectional view on line 7-7 of the device of FIG.

FIG. 8 is a sectional view on line 88 of the device of FIG.

FIG. 9 is a sectional view on line 9-9 of the device of F IG.

FIG. 10 is a bottom plan view of the device of FIG. 7;

FIG. 11 is a perspective view of a first throat plate for lockstitching;

FIG. 12 is a perspective view of a second throat plate for chainstitching;

FIG. 13 is a bottom plan view of the second throat plate of FIG. 12;

FIG. 14 is a fragmental enlarged view of the 4-4 section of FIG. 4 wherethe thread loop is released and FIG. 14a is the top view of the same;

FIG. 15 is a fragmental sectional view corresponding to FIG. 3 wherethere is fitted the first throat plate to the frame;

FIG. 16 is a fragmental sectional view corresponding to FIG. 4 where theneedle is brought down into the thread loop held by the loop retainingmember to release said loop;

FIG. 17 is an enlarged view corresponding to FIG. 3 where the threadloop taken up by the loop taker is being broadened;

FIG. 18 is a side view of the device of FIG. 17; and

FIG. 19 is an enlarged view of a bobbin case retainer according toanother embodiment of the invention correspond ing to FIG. 14.

There will now be described by reference to the appended drawings achain stitch forming device according to an embodiment of the presentinvention. A sewing machine in FIGS. 1 and 2 is an ordinary lock stitchtype. A machine frame 20 comprises a cylindrical bed 22 securely mountedon a base 21, and a standard 23 rising above said bed 22 so as tosupport a bracket arm 24 overhanging the bed 22. In the interior of theend portion of the cylindrical bed 22 is disposed the later describedloop taker. To the cylindrical bed 22 is detachably fitted a cap member25 to allow the bobbin case to be inserted into and taken out of saidbed 22. A main drive shaft 26 journaled lengthwise in the bracket arm 24drives all the moving parts of the sewing machine and may be actuated byan electric motor (not shown) through a foot treadle or the like (notshown).

A counterbalanced crank 27 on the main shaft 26 is operatively connectedthrough a connecting rod 28 to a needle bar 29 endwise slidable in asupport 30 pivoted at 31 on the bracket arm 24 and holding at its bottoma thread-carrying eyed needle 32. A needle thread takeup lever 33 isalso actuated by said crank 27 and constrained by an anchor link 34 soas to tightly stretch and slacken the needle thread alternately in timedrelationship with the endwise reciprocation of the needle 32. Thepassage of the needle thread extends from its source (not shown) to athread tension device 35 through an eyelet 36 in the takeup lever 33 andthen through appropriate guides such as a thread guide 37 on the needlebar 29 and finally to the needle eye. This arrangement for controllingthe passage of the needle thread is typical of that which is requitedfor the formation of lock stitches.

Numeral 38 in FIG. 4 denotes a loop taker shaft mounted on the frame 20rotatable around a horizontal axis parallel with the direction in whichthere is fed a work fabric 39. To one end of the shaft 38 is fitted aloop taker 41 with a loop seizing beak 40. The loop taker shaft 38 isconnected to a lower shaft 44 through a set of gears 42 and 43 (FIG. 5),said lower shaft 44 interlocking with the main drive shaft 26 by meansof a timing belt 45 (FIG. 2). The loop taker 41 is designed to rotatetwice each time the needle makes one reciprocation by means of theaforementioned arrangement. The needle and loop taker 41 are actuated insuch timed relationship that while the needle is brought downward, theloop released from the needle eye is seized by the loop taker 41 andwhile the needle is lifted, the loop seized by the loop taker isreleased therefrom. To the loop taker 41 is supported a bobbin caseretainer 47 adapted to receive an ordinary bobbin case 46. At the frontupper part of the retainer 47 is formed a recess 48 adjacent to a pointthrough which the needle passes (FIG. 3). Numeral 49 of FIG. 5represents a restraining member, the base end of which is fixed to theframe by screws 50. At one end of the restraining member is formed atongue 53 freely engaging the recess 48 to define an opening 52therewith so as to permit the passage of a loop 51 released from theloop taker 41 lifted by the thread takeup mechanism, thus preventing thebobbin case retainer 47 from rotating with the loop taker 41.

Referring to FIG. 2, there is disposed in the cylindrical bed a feed dog54 performing the known four feed motions through the slot of the laterdescribed throat plate. The feed dog advances the work fabric 39 on awork support in one direction for each endwise reciprocation of theneedle 32. The feed dog 54 is fixed on a feed bar 56 connected to a feedadvancing shaft 55, which is made to swing by a two-forked rod 53 sodisposed as to embrace a feed cam 57 on the main shaft 26, therebyimparting forward and backward movements to the feed dog 54. The feedbar 56 is operatively connected to a swing shaft 61 which is made toswing by a rod 60 embracing a feed lift eccentric 59 fixed on the maindrive shaft 26. Thus the rotation of the main shaft 26 causes the feeddog 54 to be raised. It will be appreciated that as it is conventionalin the art, the linear work feeding mechanism is timed to the reciprocation of the needle so that while the needle 32 is raised above a workfabric on the throat plate, the feed dog 54 is lifted to be advanced andwhile the needle descends, the feed dog 54 is brought beneath the throatplate back to its original position. Numeral 62 of FIG. 1 denotes a knobfor causing the feed dog 54 to perform a drop feed. Numeral 63 is amanually operable knob for controlling the advance and retraction of thefeed dog 54, and numeral 64 represents a manually operable knob forcontrolling the amplitude of the zigzag motion of the needle.

Numeral 65 of FIG. 5 shows a loop retaining member having itsintermediate portion rotatably mounted on the restraining member by astepped screw 66. One free end of the loop retaining member 65 has aretaining section 67 for temporarily holding the released loop 51 pulledup through the opening 52 by the thread takeup mechanism. As seen fromFIG. 14, one side 67a of the retaining section 67 is so formed as not toproject from one lateral portion 53a of the tongue 53 of the restrainingmember 49 disposed on that side of the bobbin case retainer 47 to whichthe recess 48 is pressed as the result of the rotation of the loop taker41. Accordingly, the loop 51 released from the loop taker 41 is liftedwithout being detained in the space between the aforesaid lateralportion 53a of the tongue 53 and the recess 52, always enabling gooduniform chain stitches to be realized without any difficulties, forexample, the slackening or resultant double'formation of chain stitches.

Numeral 68 is a spring stretched between the other end of the loopretaining member 65 and the lug 70 of the fitting member 69. The spring68 causes the loop retaining member 65 to rotate anticlockwise as shownin FIG. 5, thereby normally keeping the retaining section 67 of the loopretaining member 65 at a position above the opening 52 to hold the loopreleased from the loop taker 41. Numeral 71 in FIG. 14 is a grooveformed at the upper part of the bobbin case retainer 47 across therecess 48 so as to extend toward both sides of the recess 48 in asufficiently large size to receive the retaining section 67 of the loopretaining member 65. Above the groove 71 rises a projection wall 72 forguiding the loop 51 released from the loop taker 41 onto the retainingsection 67 of the loop retaining member 65 so as to be securely retainedthereby the projecting wall 72 has its top portion positioned lower thanthat side of the wall 73 of the bobbin case retainer 47 surrounding bothsides of the tongue 53 of the restraining member 49 freely engaging therecess 48 through which the needle passes endwise. Therefore, the loop51 released from the retaining section 67 is lifted by the takeupmechanism without any obstruction, preventing chain stitches from beingloosened or in consequence doubly formed. Moreover, the fact that oneside 67a of the retaining section 67 is so disposed as not to projectfrom one side 53a of the tongue 53, coupled with the aforementionedarrangement, assures the smooth feeding of the needle thread, alwayspermitting the formation of good chain stitches. All these facts assumegreat significance, because there is no need for any particularmachining of the parts.

The other free end of the loop retaining member 65 is bent, as shown inFIG. 3, so as to surround one end of the restraining member 49 to form abent section 74, which contacts the underside of the restraining member49 to prevent the loop retaining member 65 from being unnecessarilylifted. Accordingly, the retaining section 67 of the loop retainingmember 65 is prevented from lifting the bobbin case retainer 47 by meansof the projecting wall 72, thereby applying an excess load to the racesection between the bobbin case retainer 47 and the loop taker 41. Thisavoids the obstructed rotation of the loop taker 41 and the occurrenceof noises and wear, enabling the loop to be reliably held by the loopretaining member and chain stitches to be formed constantly.

Referring to FIG. 7, numeral 75 is an actuating plate pivoted to therestraining member 49 swingably about a pin 76 fixed to the base end ofsaid actuating plate 75. The rising section 75a of the actuating plateis contacted by the other end of the loop retaining member 65 by theaction of the spring 68, normally urging the free end 75b of theactuating plate 65 upward so as to face the underside of the feed dog54. The actuating plate 75 is swing downward as the result of thedescent of the feed dog 54 to rotate the loop retaining member 65against the action of the spring 68, thereby allowing the loop 51 heldby the loop retaining member 65 to be released therefrom by means of thethread takeup mechanism after the needle has passed through said loop51.

A pivoting member 77 for rotatably supporting the pin 76 of theactuating plate 75 between said pivoting member 77 and the backside ofthe restraining member 49 is fixed, as shown in FIGS. 7, 9 and 10, tothe backside of the restraining member 49 by a pair of screws 79 passingthrough long holes 78 perforated in the fitting member 69 andrestraining member 49 in a direction perpendicular to the position inwhich the pin 76 is set. When the screws 79 are loosened to allow thepivoting member 77 to be slightly shifted along the long holes 78 andthereafter tightened again, then the pin 76 about which the actuatingplate 75 swings is adjusted in position, thus controlling the conditionof contact between the feed dog 54 and actuating plate 75 and inconsequence the operating time of the loop retaining member 65 worked bythe actuating plate 75, so that the operating time of the loop retainingmember 65 can always be adapted for chain stitching.

Referring to FIG. 1, numeral 80 is a first throat plate detachablysupported by a stepped portion 81 formed on the peripheral edge of theopening perforated in the cylindrical bed 22. As further illustrated inFIG. 11, the first throat plate 80 has a long needle aperture 82 adaptedfor zigzag lock stitching which extends in a direction perpendicular tothat in which there if fed a work fabric, and also narrow slots 33 toallow the feed dog 54 to pass therethrough. To the underside of one endof the first throat plate 80 is fitted an elastic plate 85 to preventsaid throat plate 80 from being lifted by engaging the underside of theperipheral edge of the opening of the cylindrical bed 22. The undersideof the other end of the first throat plate 80 is fitted by screws 88 and89 with an elastic plate 87 elastically engaging a projection 86 on theperipheral edge of the opening of the cylindrical bed 22. One of thescrews indicated by 89 engages, as shown in FIG. 15, the actuating plate75 when the first throat plate 80 is fitted to the frame so as to causethe actuating plate 75 to rotate up to the point (indicated by a solidline) where it is not operated as the result of the descent of the feeddog 54. Accordingly, the screw 89 constitutes a sort of stop projectionfor arresting the loop retaining member at a point where it can not holdthe loop 51 released from the loop taker 41. Thus the lock stitchforming mechanism is brought to an operative state.

Referring to FIGS. 12 and 13, numeral 90 denotes a second throat platedetachably fitted to the frame in place of the first throat plate 80.The second throat plate has a long needle aperture 91 extending in thedirection in which there is fed a work fabric. When the loop releasedfrom the loop retaining member 65 is lifted by the thread takeupmechanism, the aforesaid position of the needle aperture-91 prevents thechain stitched thread to be insufficiently tightened due to theresistance to which it is subjected while passing through the needleaperture 91. Numeral 92 is a depression formed in continuation of theneedle aperture 91 to improve tightening of a chain stitched thread. Thesame parts of the second throat plate 90 as those of the first throatplate 80 shown in FIG. 11 are denoted by the same numerals anddescription thereof is omitted. The second throat plate 90 is notprovided with a stop projection corresponding to the screw 89 of thefirst throat plate 80. Accordingly, when the second throat plate 90 isfitted to the frame, there is reestablished an operative relationbetween the feed dog 54 and actuating plate 75 to permit the operationof the loop retaining member 65 so as to hold the loop released from theloop taker 41. To the suspended strip 93 of the restraining member 49 ispivoted a manually operable lever 94 for disengaging the throat plate bymeans of a stepped screw 95 (FIG. 6). One end 96 of the lever 94 extendsso as to face the underside of that part of the throat plate where theengaging elastic plate 87 is positioned, and the other end of the lever94 constitutes an operating knob 97. Numeral 98 represents a springstretched across the throat plate disengaging lever 94 and restrainingmember 49. The spring 98 causes the lever 94 to rotate anticlockwise asshown in FIG. 6. In the foregoing embodiment the restraining member 49is fitted with all the loop retaining member 65, actuating plate 75 andthroat plate disengaging lever 94. Since all these members can bearranged into a single unit, there is obtained great advantage inassembling and manufacturing a sewing machine.

There will now be described the application of a chain stitch formingdevice according to the aforementioned embodiment and the manner inwhich there are formed chain stitches. FIGS. 3 to 6 represent the statewhere the loop 51 released from the loop seizing beak 40 of the looptaker 41 is lifted by the thread takeup mechanism and, after passingbetween the tongue 53 and recess 48, is held by the retaining section 67of the loop retaining member 65. At this time, the feed dog 54 is in arising position and disengaged from the actuating plate 75. It will beapparent, however, that the second throat plate 90 for chain stitchingis not provided with a screw 89 like the first throat plate 80, so thatwhen the feed dog 54 descends, the actuating plate 75 is brought to anoperative state.

When there is carried forward a work fabric 39 one stitch pitch by thefeed dog 54, and the needle 32 is brought down again, as shown in FIG.16, into the loop 51, then the underside of the feed dog 54 engages thefree end 75b of the actuating plate 75 as the result of the descent ofthe feed dog 54, causing the actuating plate 75 to swing downward and inconsequence the loop 51 held by the retaining section 67 to be released.

As the sewing operation goes on, a loop freshly formed by a descendingneedle 32 is taken up by the loop seizing beak 40 of the loop taker 41in preparation for the formation of a succeeding chain stitch. As afresh loop 51 is gradually broadened by the loop taker 41, the precedingloop is pulled into the work fabric 39 to form a chain stitch, as shownin FIGS. 17 and 18. Later when the feed dog 54 is lifted again, the loopretaining member 65 is brought back to its original position by theaction of the spring 68 and the retaining section 67 of said member 65is inserted into the groove 71 to be brought again to a state of holdingthe loop 51.

When, upon completion of the desired chain stitching, it is desired touse the sewing machine for the original lock stitching, the cap member25 of the cylindrical bed is opened, and the knob 97 on the manuallyoperable throat plate disengaging lever 94 is depressed with the fingerto rotate the lever 94 against the action of the spring 98. Then theengaging elastic plate 87 of the second throat plate 90 is released fromthe projection 86, causing said plate 90 to be forcibly pushed outward.All that is required, therefore, is to remove the second throat plate 90and instead insert the previously provided first throat plate for normallock stitching. When the first throat plate 80 is inserted, it is firstguided to the stepped part 81 of the cylindrical bed 22 and the elasticplate 85 is pressed in place so as to engage the underside of theperipheral edge of the opening for said throat plate. When that part ofthe first throat plate 80 where the engaging elastic plate 87 ispositioned is depressed, said elastic plate 87 engages the projection86, causing the first throat plate 80 to be set in place as shown inFIG. 15. At this time the screw 89 of the first throat plate 80 engagesthe actuating plate 75 to swing it from the position indicated by thetwo-dot-dash line to that of the solid line, so that the actuating plate7 5 ceases to be operated despite the movement of the feed dog 54.Therefore, the loop retaining member 65 is operated in the same manneras in chain stitching and the retaining section 67 is brought to rest,as shown in FIG. 16, independently of the loop passing through theopening between the tongue 53 and recess 48. Accordingly, the normallock stitching can be commenced again by feeding the lower thread intothe bobbin case 46.

' Where it is desired to carry out chain stitching again, it is onlyrequired to replace the first throat plate 80 with the second throatplate by the same operation as used in exchanging the second for thefirst throat plate.

With the device according to the aforesaid embodiment, when the knob 62is operated to bring down the feed dog 54, the actuating plate 75 swingsdownward to arrest the loop retaining member. Therefore, when it isdesired to perform embroidering with the normal lock stitches bylowering the feed dog 54, there is no need to replace the second throatplate 90 with the first throat plate 80, but it is sufficient to operateonly the knob 62.

FIG. 19 shows the part of FIG. 14 modified according to anotherembodiment of the invention. There is formed a groove across the recess48 so as to extend toward its both sides, and there is fitted into thegroove 100 the retaining section 67 of the loop retaining member 65, thewall 101 of the groove 100 serving as the aforementioned projecting wall72. The embodiment of FIG. 19 eliminates the necessity of forming saidprojecting wall 72 above the recess 48, so that when this embodiment isused for the original lock stitching, the loop released from the looptaker 41 and lifted by the takeup mechanism passes through the recess 43exactly in the same manner as in the prior art lock stitch sewingmachine, thus exerting no hannful effect on such stitching.

As mentioned above, the present invention provides a very advantageouschain stitch forming device for the general user of a sewing machine,thus widely broadening the application of an original lock stitch sewingmachine.

What is claimed is:

1. A chain stitch forming device for a lock stitch sewing machineincluding a frame having a work support perforated with a needleaperture,

a thread-carrying eyed needle supported by the frame above the worksupport for endwise reciprocation through the needle aperture,

a needle thread takeup mechanism mounted on the frame for alternatelytightening and loosening the needle thread in timed relationship withthe endwise reciprocation of the needle,

a loop taker so mounted on the frame as to rotate about an axis,

a bobbin case retainer supported in the loop taker and adapted toaccommodate an ordinary bobbin case therein,

stop means provided between the frame and bobbin case retainer so as toprevent the bobbin case retainer from making a circular movementtogether with the loop taker near the point through which the needlepasses endwise,

means for driving the needle and loop taker in such timed relationshipthat while the needle is brought down the loop coming out of the needleeye is seized by the loop taker and while the needle is lifted theseized loop is released from the loop taker, said stop means beingprovided with a recess and tongue connection freely engaging each otherso as to form an opening therebetween for permitting the passage of thereleased loop pulled up by the needle thread takeup mechanism and,

means for linearly feeding a work fabric carried on the work support ina prescribed direction from the needle aperture during each endwisereciprocation of the needle, characterized in that the device furthercomprises a movable loop retaining member having a retaining section fortemporarily retaining the released ioop pulled up through the opening bythe thread takeup mechanism,

means connected to the loop retaining member for normally setting theretaining section of the loop retaining member in a loop retainingposition above the opening so as to hold the released loop, and

operating means for moving the loop retaining member from the loopretaining position to allow the thread loop held on the retainingsection to be pulled off therefrom by the thread takeup mechanism afterthe needle passes through the loop in the next downward movement.

2. A device according to claim ll wherein the bobbin case retainer isprovided with a projecting wall for guiding the released loop so as tosecurely hold it by the retaining section ofthe loop retaining member.

3. A device according to claim ll wherein there is disposed between theoperating means and loop retaining member means for controlling the timeat which the loop retaining member is actuated by the operating means.

4. A chain stitch forming device for a lock stitch sewing machineincluding a frame having a work support perforatedwith a needleaperture,

a thread-carrying eyed needle supported by the frame above the worksupport for endwise reciprocation through the needle aperture,

a needle thread takeup mechanism mounted on the frame for alternatelytightening and loosening the needle thread in timed relationship withthe endwise reciprocation of the needle,

a loop taker so mounted on the frame as to rotate about an axis,

a bobbin case retainer supported in the loop taker and adapted toaccommodate an ordinary bobbin case therein,

a restraining member whose base end is fixed to the frame to prevent thebobbin case from making a circular movement together with the looptaker,

means for driving the needle and loop taker in such timed relationshipthat while the needle is brought down the loop coming out of the needleeye is seized by the loop taker and while the needle is lifted theseized loop is released from the loop taker,

a recess and tongue connection freely engaging each other positionedbetween the end of the restraining member and bobbin case retainer so asto form an opening therebetween for permitting the passage of thereleased loop pulled up by the needle threadtakeup mechanism, and

means for linearly feeding a work fabric carried on the work support ina prescribed direction from the needle aperture during each endwisereciprocation of the needle, characterized in that the device furthercomprises a loop retaining member rotatably mounted on the restrainingmember and having a loop retaining section formed at its free end fortemporarily retaining the released loop pulled up through the opening bythe thread takeup mechanism,

means connected to the loop retaining member for allowing the retainingsection of the loop retaining member to be normally set in a loopretaining position above the opening so as to hold the released loop,and

operating means for moving the loop retaining member from the loopretaining position to allow the thread loop held on the retainingsection to be pulled off therefrom by the thread takeup mechanism afterthe needle passes through the loop in the next downward moment. i

5. A device according to claim 4 wherein there is provided stop meansbetween the free end of the loop retaining member and restraining memberso as to prevent said free end from being raised.

6. A device according to claim 5 wherein the free end of the loopretaining member is so bent as to surround the restraining member andcontact the underside of the restraining member.

7. A chain stitch forming device for a lock stitch sewing machineincluding a frame having a work support perforated with a needleaperture,

a thread-carrying eyed needle supported by the frame above the worksupport for endwise reciprocation through the needle aperture,

a needle thread takeup mechanism mounted on the frame for alternatelytightening and loosening the needle thread in timed relationship withthe endwise reciprocation of the needle,

a loop taker so mounted on the frame as to rotate about an axis,

a bobbin case retainer supported in the loop taker and adapted toaccommodate an ordinary bobbin case therein, said bobbin case retainerbeing provided with a recess near the point through which the needlepasses endwise, a restraining member having its base end fixed to theframe for preventing the bobbin case retainer from making a circularmovement together with the loop taker and provided at the end with atongue freely engaging the recess so as to define an opening therewithfor permitting the passage of the released loop pulled up by the threadtakeup mechanism,

means for driving the needle and loop taker in such timed relationshipthat while the needle is brought down the loop coming out of the needleeye is seized by the loop taker and while the needle is lifted theseized loop is released from the loop taker, and

means for linearly feeding a work fabric carried on the work support ina prescribed direction from the needle aperture during each endwisereciprocation of the needle, characterized in that the device furthercomprises a movable loop retaining member having a retaining section fortemporarily retaining the released loop pulled up through the opening bythe thread takeup mechanism,

means connected to the loop retaining member for allowing the retainingsection of the loop retaining member to be normally set in a loopretaining position above the opening so as to hold the released loop,and

means for moving the loop retaining member from the loop retainingposition for allowing the thread loop held by the loop retaining sectionto be pulled off therefrom by the thread takeup mechanism after theneedle passes through the loop in the next downward movement.

8. A device according to claim 7 wherein the bobbin case retainer isprovided with a projecting wall for guiding the released loop in to theretaining section of the loop retaining member so as to securely hold itthereon, the top of said projecting wall being positioned below thatpart of the wall of the bobbin case retainer surrounding both sides ofthe tongue of the restraining member through which the needle passesendwise.

9. A device according to claim 7 wherein one side of the retainingsection of the loop retaining member is so formed as not to project fromone side of the tongue of the restraining member to which there ispressed the recess of the bobbin case retainer each time the loop takerrotates.

into the groove the retaining section of the loop retaining member.

1. A chain stitch forming device for a lock stitch sewing machine including a frame having a work support perforated with a needle aperture, a thread-carrying eyed needle supported by the frame above the work support for endwise reciprocation through the needle aperture, a needle thread takeup mechanism mounted on the frame for alternately tightening and loosening the needle thread in timed relationship with the endwise reciprocation of the needle, a loop taker so mounted on the frame as to rotate about an axis, a bobbin case retainer supported in the loop taker and adapted to accommodate an ordinary bobbin case therein, stop means provided between the frame and bobbin case retainer so as to prevent the bobbin case retainer from making a circular movement together with the loop taker near the point through which the needle passes endwise, means for driving the needle and loop taker in such timed relationship that while the needle is brought down the loop coming out of the needle eye is seized by the loop taker and while the needle is lifted the seized loop is released from the loop taker, said stop means being provided with a recess and tongue connection freely engaging each other so as to form an opening therebetween for permitting the passage of the released loop pulled up by the needle thread takeup mechanism and, means for linearly feeding a work fabric carried on the work support in a prescribed direction from the needle aperture during each endwise reciprocation of the needle, characterized in that the device further comprises a movable loop retaining member having a retaining section for temporarily retaining the released loop pulled up through the opening by the thread takeup mechanism, means connected to the loop retaining member for normally setting the retaining section of the loop retaining member in a loop retaining position above the opening so as to hold the released loop, and operating means for moving the loop retaining member from the loop retaining position to allow the thread loop held on the retaining section to be pulled off therefrom by the thread takeup mechanism after the needle passes through the loop in the next downward movement.
 2. A device according to claim 1 wherein the bobbin case retainer is provided with a projecting wall for guiding the released loop so as to securely hold it by the retaining section of the loop retaining member.
 3. A device according to claim 1 wherein There is disposed between the operating means and loop retaining member means for controlling the time at which the loop retaining member is actuated by the operating means.
 4. A chain stitch forming device for a lock stitch sewing machine including a frame having a work support perforated with a needle aperture, a thread-carrying eyed needle supported by the frame above the work support for endwise reciprocation through the needle aperture, a needle thread takeup mechanism mounted on the frame for alternately tightening and loosening the needle thread in timed relationship with the endwise reciprocation of the needle, a loop taker so mounted on the frame as to rotate about an axis, a bobbin case retainer supported in the loop taker and adapted to accommodate an ordinary bobbin case therein, a restraining member whose base end is fixed to the frame to prevent the bobbin case from making a circular movement together with the loop taker, means for driving the needle and loop taker in such timed relationship that while the needle is brought down the loop coming out of the needle eye is seized by the loop taker and while the needle is lifted the seized loop is released from the loop taker, a recess and tongue connection freely engaging each other positioned between the end of the restraining member and bobbin case retainer so as to form an opening therebetween for permitting the passage of the released loop pulled up by the needle thread takeup mechanism, and means for linearly feeding a work fabric carried on the work support in a prescribed direction from the needle aperture during each endwise reciprocation of the needle, characterized in that the device further comprises a loop retaining member rotatably mounted on the restraining member and having a loop retaining section formed at its free end for temporarily retaining the released loop pulled up through the opening by the thread takeup mechanism, means connected to the loop retaining member for allowing the retaining section of the loop retaining member to be normally set in a loop retaining position above the opening so as to hold the released loop, and operating means for moving the loop retaining member from the loop retaining position to allow the thread loop held on the retaining section to be pulled off therefrom by the thread takeup mechanism after the needle passes through the loop in the next downward moment.
 5. A device according to claim 4 wherein there is provided stop means between the free end of the loop retaining member and restraining member so as to prevent said free end from being raised.
 6. A device according to claim 5 wherein the free end of the loop retaining member is so bent as to surround the restraining member and contact the underside of the restraining member.
 7. A chain stitch forming device for a lock stitch sewing machine including a frame having a work support perforated with a needle aperture, a thread-carrying eyed needle supported by the frame above the work support for endwise reciprocation through the needle aperture, a needle thread takeup mechanism mounted on the frame for alternately tightening and loosening the needle thread in timed relationship with the endwise reciprocation of the needle, a loop taker so mounted on the frame as to rotate about an axis, a bobbin case retainer supported in the loop taker and adapted to accommodate an ordinary bobbin case therein, said bobbin case retainer being provided with a recess near the point through which the needle passes endwise, a restraining member having its base end fixed to the frame for preventing the bobbin case retainer from making a circular movement together with the loop taker and provided at the end with a tongue freely engaging the recess so as to define an opening therewith for permitting the passage of the released loop pulled up by the thread takeup mechanism, means for driving the needle and loop taker in such timed relaTionship that while the needle is brought down the loop coming out of the needle eye is seized by the loop taker and while the needle is lifted the seized loop is released from the loop taker, and means for linearly feeding a work fabric carried on the work support in a prescribed direction from the needle aperture during each endwise reciprocation of the needle, characterized in that the device further comprises a movable loop retaining member having a retaining section for temporarily retaining the released loop pulled up through the opening by the thread takeup mechanism, means connected to the loop retaining member for allowing the retaining section of the loop retaining member to be normally set in a loop retaining position above the opening so as to hold the released loop, and means for moving the loop retaining member from the loop retaining position for allowing the thread loop held by the loop retaining section to be pulled off therefrom by the thread takeup mechanism after the needle passes through the loop in the next downward movement.
 8. A device according to claim 7 wherein the bobbin case retainer is provided with a projecting wall for guiding the released loop in to the retaining section of the loop retaining member so as to securely hold it thereon, the top of said projecting wall being positioned below that part of the wall of the bobbin case retainer surrounding both sides of the tongue of the restraining member through which the needle passes endwise.
 9. A device according to claim 7 wherein one side of the retaining section of the loop retaining member is so formed as not to project from one side of the tongue of the restraining member to which there is pressed the recess of the bobbin case retainer each time the loop taker rotates.
 10. A device according to claim 7 wherein there is formed a groove at the top of the bobbin case retainer across the recess so as to extend toward both sides thereof and there is fitted into the groove the retaining section of the loop retaining member. 